U.S. patent application number 12/415157 was filed with the patent office on 2010-04-08 for system, method and apparatus for exploration.
Invention is credited to Chester A. Wallace.
Application Number | 20100086180 12/415157 |
Document ID | / |
Family ID | 42075857 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100086180 |
Kind Code |
A1 |
Wallace; Chester A. |
April 8, 2010 |
SYSTEM, METHOD AND APPARATUS FOR EXPLORATION
Abstract
In accordance with one embodiment, a method of locating mineral
deposits suitable for production comprises obtaining via a computer
an image of an area of land, determining from the image at least
one fluid-expulsion structure present on the land, designating an
area proximate the fluid-expulsion structure as a mineral
exploration location; while in accordance with another embodiment a
method of locating a hydrocarbon reservoir suitable for production
is described which comprises obtaining via a computer an image of
an area of land, determining from the image at least one
fluid-expulsion structure present on the land, and designating an
area proximate the fluid-expulsion structure as a hydrocarbon
exploration location.
Inventors: |
Wallace; Chester A.;
(Morrison, CO) |
Correspondence
Address: |
SWANSON & BRATSCHUN, L.L.C.
8210 SOUTHPARK TERRACE
LITTLETON
CO
80120
US
|
Family ID: |
42075857 |
Appl. No.: |
12/415157 |
Filed: |
March 31, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61103856 |
Oct 8, 2008 |
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Current U.S.
Class: |
382/109 |
Current CPC
Class: |
G01V 9/00 20130101 |
Class at
Publication: |
382/109 |
International
Class: |
G06K 9/00 20060101
G06K009/00 |
Claims
1. A method of locating mineral deposits suitable for production,
the method comprising: obtaining via a computer an image of an area
of land; determining from the image at least one fluid-expulsion
structure present on the land; designating an area proximate the
fluid-expulsion structure as a mineral exploration location.
2. The method as claimed in claim 1 wherein the fluid expulsion
structure is a breccia pipe.
3. The method as claimed in claim 1 wherein the fluid expulsion
structure is a sand injectite.
4. The method as claimed in claim 1 wherein the determining from
the image at least one fluid-expulsion structure comprises
determining a cluster of fluid-expulsion structures.
5. The method as claimed in claim 1 wherein the obtaining the image
comprises obtaining a satellite image of the area of land.
6. The method as claimed in claim 1 wherein the obtaining the image
comprises obtaining an aerial photograph.
7. The method as claimed in claim 1 wherein the obtaining the image
comprises obtaining a satellite image of the area of land with a
ground sample distance resolution of less than 20 meters.
8. The method as claimed in claim 1 wherein the obtaining the image
comprises obtaining a satellite image of the area of land with a
ground sample distance resolution of less than 5 meters.
9. The method as claimed in claim 1 wherein the mineral exploration
location is targeted within the fluid-expulsion structure.
10. The method as claimed in claim 1 and further comprising:
determining the location of a particular metal deposit via a
metal-maturity window.
11. A method of locating a hydrocarbon reservoir suitable for
production, the method comprising: obtaining via a computer an
image of an area of land; determining from the image at least one
fluid-expulsion structure present on the land; designating an area
proximate the fluid-expulsion structure as a hydrocarbon
exploration location.
12. The method as claimed in claim 11 wherein the fluid-expulsion
structure is a breccia pipe.
13. The method as claimed in claim 11 wherein the fluid-expulsion
structure is a sand injectite.
14. The method as claimed in claim 11 wherein the determining from
the image at least one fluid-expulsion structure comprises
determining a cluster of fluid-expulsion structures.
15. The method as claimed in claim 11 wherein the obtaining the
image comprises obtaining a satellite image of the area of
land.
16. The method as claimed in claim 11 wherein the obtaining the
image comprises obtaining an aerial photograph.
17. The method as claimed in claim 11 wherein the obtaining the
image comprises obtaining a satellite image of the area of land
with a ground sample distance resolution of less than 20
meters.
18. The method as claimed in claim 11 wherein the obtaining the
image comprises obtaining a satellite image of the area of land
with a ground sample distance resolution of less than 5 meters.
19. The method as claimed in claim 11 wherein the hydrocarbon
exploration location is targeted within strata proximate to the
fluid expulsion structure.
20. The method as claimed in claim 11 and further comprising:
determining the time of hydrocarbon generation and a migration
direction to establish historical progression of fluids through
aquifers, so as to establish which fluid-expulsion structures among
a plurality of fluid expulsion structures are most likely to
contain hydrocarbons.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) of provisional application Ser. No. 61/103,856, filed Oct.
8, 2008 for "SYSTEM, METHOD AND APPARATUS FOR MINERAL EXPLORATION"
in its entirety and for all purposes.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH OR DEVELOPMENT
[0002] NOT APPLICABLE
REFERENCE TO A "SEQUENCE LISTING," A TABLE, OR A COMPUTER PROGRAM
LISTING APPENDIX SUBMITTED ON A COMPACT DISK
[0003] NOT APPLICABLE
BACKGROUND
[0004] Mineral and hydrocarbon exploration is a time consuming and
expensive process. It can involve travel to remote areas and
extensive governmental permitting processes and negotiation with
private landowners. As a result, the targeting of prospective
exploration sites is made carefully. Despite these careful
attempts, exploration at targeted sites often results in failure.
Either the resources discovered are insufficient for further
development of the site to make economic sense or no resources are
discovered at the site.
[0005] Given the vast resources of mining and hydrocarbon
exploration companies, it is clear that those companies are
currently using the best techniques that they currently know about
to try and target new sites for mineral and/or hydrocarbon
development. Despite those best efforts, however, those companies
have not yet discovered the techniques claimed herein. Thus, the
following disclosure is believed to set forth patentable
embodiments.
SUMMARY
[0006] In accordance with one embodiment, a method of locating
mineral deposits suitable for production is disclosed. The method
comprises obtaining via a computer an image of an area of land;
determining from the image at least one fluid-expulsion structure
present on the land; and designating an area proximate the
fluid-expulsion structure as a mineral exploration location.
[0007] In accordance with another embodiment, a method of locating
a hydrocarbon reservoir suitable for production is disclosed. The
method comprises obtaining via a computer an image of an area of
land; determining from the image at least one fluid-expulsion
structure present on the land; and designating an area proximate
the fluid-expulsion structure as a hydrocarbon exploration
location.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a map showing three areas in the U.S.
that contain prominent fluids-expulsion structures
[0009] FIGS. 2A, 2B, 2C, and 2D illustrate a schematic rendition
that show four examples of the role of tectonic control of sediment
burial and metal transport in sedimentary basins.
[0010] FIG. 3 illustrates general relations among burial depth of
sediment, temperature increase during progressive burial, pressure
increase during continuing burial, dewatering periods caused by
increasing pressure and temperature, hydrocarbon maturity, and
metal-maturity windows.
[0011] FIG. 4 illustrates a seismic profile of large-scale,
interconnected sand injectites, offshore United Kingdom, in the
Faeroe-Shetland Basin.
[0012] FIG. 5 illustrates a seismic profile of igneous sills
intruded into a clastic sequence offshore United Kingdom, Rockall
Basin.
[0013] FIG. 6 illustrates a seismic profile across three
dissolution pipes in the eastern Mediterranean Levant Basin.
[0014] FIG. 7 illustrates a seismic profile of a blowout pipe from
offshore Namibia.
[0015] FIG. 8 illustrates a seismic profile of a seepage pipe at
the arrow (offshore Scotland in the Faeroe-Shetland Basin).
[0016] FIG. 9 illustrates a flowchart demonstrating a method of
targeting a mineral exploration location in accordance with one
embodiment of the invention.
[0017] FIGS. 10A and 10B illustrate a flowchart demonstrating a
method of targeting a mineral exploration location in accordance
with another embodiment of the invention.
[0018] FIG. 11 illustrates a flowchart demonstrating a method of
targeting a hydrocarbon exploration location in accordance with one
embodiment of the invention.
[0019] FIGS. 12A and 12B illustrate a flowchart demonstrating a
method of targeting a hydrocarbon exploration location in
accordance with another embodiment of the invention.
[0020] FIG. 13 illustrates a diagram of a system for obtaining
images of prospective exploration targets in accordance with one
embodiment of the invention.
[0021] FIG. 14 illustrates a block diagram of a computer that can
be used to implement a computerized device in accordance with one
embodiment of the invention.
DETAILED DESCRIPTION
Overview
[0022] In accordance with one embodiment of the invention, the
identification of ancient fluid-expulsion structures can be used to
identify preferred locations for mineral deposits and/or
hydrocarbon reservoirs. This report demonstrates that ancient
fluid-expulsion structures are preferred locations for mineralized
breccia, stratabound mineral deposits, and hydrocarbon reservoirs
that can contain billions or trillions of dollars in metals or oil.
Ancient fluid-expulsion structures represent important migration
pathways for warm, metal-bearing, reduced, saline fluids and
hydrocarbons in subsiding sedimentary basins. These features can be
focal sites for reduction-oxidation chemical reactions that produce
mineral deposits, making these structures highly prospective for
stratabound mineral deposits. Where seals are preserved in these
structures and in host strata, significant oil or gas accumulations
may occur. Not all fluid-expulsion structures are mineralized or
contain hydrocarbon reservoirs, but these structures are easy to
find in ancient sedimentary basins using satellite images available
to the public. These "faucets" were important controls of
fluid-migration pathways in ancient sedimentary basins, and to date
their role has not been understood by the mineral exploration
industry nor by hydrocarbon explorers. The potential for these
structures to contain large metal deposits has not been recognized
by the mineral exploration industry, and most of the hydrocarbon
exploration industry relates these structures to astroblemes and
discounts the extraordinary resource potential. Sedimentary basins
on the Earth that produced oil or gas have the potential to contain
fluid-expulsion structures. The global distribution of
fluid-expulsion structures in ancient sedimentary basins opens a
vast new terrain to mineral and hydrocarbon exploration using very
precise and simple methods to focus ground exploration efforts. The
existence and importance of these structures has not been
recognized by the mineral exploration industry nor by the
hydrocarbon exploration industry. Nor has the potential for these
structures to contain large metal deposits and hydrocarbon deposits
been recognized.
[0023] Seismic profiles from subsea oil-producing basins show
several types of brine and oil expulsion structures that are
described in terms of disrupting seals on reservoirs. In subsea
sedimentary basins, seal penetration in overpressured reservoirs
produces breccia pipes and fluid-escape structures that are
commonly cylindrical. Evaporite dissolution produces collapse
breccia pipes through which brine and hydrocarbons can escape
upward. In overpressured fluid systems, igneous sills can be
disrupted and entrained in fluid-expulsion pipes, fluidized sand
can be injected upward to break a reservoir seal, or overpressured
fluids can "blowout" reservoir seals to inject fluidized sediment,
brine, and hydrocarbons into overlying sediment. These
fluid-expulsion structures can remain open to migrating brine, oil,
and gas for tens of millions of years. Metal-bearing, warm,
reduced, saline brine associated with migrating or trapped
hydrocarbon can be injected upward through fluid-expulsion
structures to cooler environments where oxidized sediment can
chemically react with reduced fluid to form mineral deposits in
pipes and in permeable strata invaded by reduced fluids. In
addition, a ruptured seal can permit oil and gas to migrate upward
through the break and enter permeable strata adjacent to the
fluid-expulsion structure or form secondary reservoirs within the
porous pipe if seals exist.
[0024] During subsidence of a sedimentary basin, temperatures
increase, formation water becomes more saline, organic compounds
begin to form, and metals leach from metal-bearing sediment into
the warm brine. Metals leach into brines in a specific order
determined by the thermodynamic behavior of metal ions. The concept
of metal-maturity windows summarizes the sequence and temperatures
of metal leaching. Low-temperature fluids contain more uranium,
vanadium, copper, silver, gold and platinum group metals than do
higher temperature formation fluids, which are rich in lead and
zinc. The temperature range in which most metals leach into brine
is similar to temperature ranges that change kerogen into oil and
gas. Low-temperature metamorphic fluids expelled from sedimentary
basins contain high concentrations of gold, copper, and cobalt, but
temperatures in this range crack hydrocarbons.
[0025] Three examples illustrate the importance of fluid-expulsion
structures in forming mineral deposits: (1) Northwestern Arizona
which is dominated by karst-breccia fluid-expulsion structures rich
in uranium, vanadium, and copper; (2) San Rafael Swell where sand
injectites provided avenues for warm, reducing, saline brine and
hydrocarbons under high pressure that deposited uranium, vanadium,
and copper; and (3) Mid-Continent of the U.S. where large diameter
fluid-expulsion structures were part of the base-metal sulfide
mineralization system.
[0026] In northwestern Arizona, in the vicinity of the Grand
Canyon, more than 1,000 small diameter breccia pipes have been
identified, and these pipes occur in clusters. Not all pipes are
mineralized, but some pipes that are mineralized contain
significant resources of uranium, vanadium, copper, and silver.
Although most mineral deposits occur in breccia pipes, rich
stratabound deposits have produced millions of pounds of U3O8 from
permeable strata adjacent to the pipes. Common trace elements are
chromium, molybdenum, lead, zinc, strontium, and antimony, and some
can be present is substantial concentrations. Asphalt is common in
traces in these pipes, so some oil was in the brine. About 18 mines
have produced uranium, vanadium, and copper as the main metals in
northwestern Arizona. The estimated mean value for undiscovered
uranium is 1,300,000 tons of U3O8 over 16,728 sq mi in the Grand
Canyon region.
[0027] On the San Rafael Swell in east-central Utah, three widely
separated clusters of "collapse" pipes contain high concentrations
of uranium and copper. These pipes are sand injectites that form
breccia, and the injectites penetrated more than 1,600 ft (about
490 m) before host sand, silt, and mud were completely lithified.
The injected sand and breccia provided an upward fluid pathway for
metal-bearing, reduced, warm brine that deposited uranium,
vanadium, and copper, and minor oil in the sand injectites and in
permeable strata of the Moenkopi and Chinle Formations where
stratabound mineral deposits formed. About 7,000,000 lbs (3,500
tons) of uranium was produced by mines on the San Rafael Swell, but
this amount of uranium may represent only a small fraction of the
original metal contained in stratabound ore deposits because
erosion eliminated much of the rock that may have contained
uranium, vanadium, and copper. Although uranium and vanadium have
been the primary focus of exploration and production on the San
Rafael Swell, these deposits are multi-metal stratabound
occurrences, and copper, gold, and platinum group metals add value
to ore.
[0028] In the Mid-Continent region, fluid-expulsion dikes and pipes
occur in clusters, and some structures are several miles in
diameter. Hicks Dome, in southern Illinois, is an anticlinal
feature that is intruded by breccia dikes that contain igneous
rocks and limestone in a sandy matrix. Hicks Dome and the nearby
Cave-In-Rock mining district produce fluorspar, galena, and
sphalerite ore from breccia dikes and from stratabound deposits
adjacent to breccia dikes. Although no circular features occur at
Hicks Dome, four prominent circular features occur 15 ml (about 24
km) to the west. Serpent Mound, in southwestern Ohio, is about 5 ml
(about 8 km) in diameter, and this structure has an uplifted
central plug, a prominent moat, and an uplifted rim. Breccia is
prominent in the plug and rim, and this structure has been
considered an impact structure in recent studies, but further
analysis suggests that it is a fluid-expulsion structure. Breccia
is mineralized by sphalerite. Stratabound sphalerite deposits occur
along bedding planes. This structure is probably related to
Mississippi Valley-type lead and zinc deposits in this region.
Serpent Mound is one of four probable fluid-expulsion structures
that occur in a cluster within an area of 125 sq mi (about 327 sq
km) in a north-south oriented mineralized zone.
[0029] New clusters of probable fluid-expulsion structures have
been identified by examining satellite images in the Mid-Continent
region. Near a described circular structure at Versailles, Ky., two
other circular features occur. Between Versailles and Jeptha Knob,
Ky., a large circular feature has been identified at Harrisonville,
Ky. Muldraugh Dome is a described circular feature in northern
Kentucky, and two other features occur south of the Dome.
Approximately 15 ml (about 24 km) northwest from Muldraugh Dome are
three circular features cut by the Ohio River near Maukport, Ind.,
and these features range from 1.5 to 2.5 ml (about 2.5 to 4 km) in
diameter, and nearby a fourth, smaller circular feature is only 0.9
ml (about 1.5 km) in diameter. These potential fluid-expulsion
structures are probably related to regional brine and hydrocarbon
migration from the Appalachian Basin located to the east. None of
the newly identified structures are likely to have been explored
for stratabound mineral deposits, and possible relations to
hydrocarbon reservoirs are not likely to have been evaluated.
[0030] Although the focus of this explication is mainly applied to
locating prospective sites for stratabound mineral deposits, a
corollary proposition is that these structures are also potential
hydrocarbon traps. Fluid-expulsion structures may trap hydrocarbons
where seals occur above porous breccia and in stratigraphic traps
adjacent to breccia pipes in permeable host strata. A brief
evaluation of potential fluid-expulsion structures that contain
hydrocarbons indicates that estimated reserves of oil trapped in
and adjacent to expulsion structures are 50 MMBO at the Ames
structure in Oklahoma, 10 MMBO at Red Wing Creek in North Dakota,
600 MMBO at Cass Co. Michigan, and 700 MMBO at the Lima structure
in Michigan. Most of these structures have been misidentified as
meteorite impact features. Exploration for new fluid-expulsion
structures near known hydrocarbon-producing structures could be
accomplished at low cost because secondary traps are generally
shallow.
[0031] Several options are available to support exploration for
stratabound mineral deposits and for oil or gas reservoirs. For
stratabound mineral exploration two options that could be
integrated into exploration programs are: (1) Conduct a methodical,
global examination of all land-based, oil-producing basins where a
company has on-going mining operations, exploration licenses, or
claim blocks to locate possible fluid-expulsion structures that may
contain stratabound mineral deposits or mineralized breccia pipes;
(2) Examine all land-based, oil-producing basins to evaluate the
volume of hydrocarbon productivity (Total Petroleum System
Analysis), with the presumption that basins with the greatest
volume of oil also generated the largest volume of metal-bearing
brine. Basins that produced the most oil have the best
prospectivity to have generated numerous fluid-expulsion structures
and attendant stratabound mineral deposits. A third option for
stratabound mineral exploration would be to conduct a methodical,
global examination of oil-producing basins without regard to amount
of oil production to compensate for basins that have potential high
oil-productivity, but that have been recently discovered. A fourth
option for stratabound mineral exploration involves training staff
to employ the concepts to which the company has purchased access.
Exploration for oil and gas using these concepts also has several
options: (1) Conduct a methodical, global examination of land-based
sedimentary basins to locate possible fluid-expulsion structures
that may contain oil or that may have peripheral reservoirs; (2)
The presumption of a link between the volume of oil produced in a
basin and the number of potential fluid-expulsion structures and
attendant hydrocarbon reservoirs appears valid for oil and gas
exploration as well, so those basins with the greatest production
should be investigated first; (3) Determine the time of hydrocarbon
generation and migration directions to establish progression of
fluids through aquifers, which can be used to establish which
fluid-expulsion structures are most likely to contain hydrocarbons;
and (3) A training option for company staff to employ these
concepts for hydrocarbon exploration is possible.
[0032] Fluid-Expulsion Structures
[0033] Fluid-expulsion structures have a global importance to
mineral and oil exploration because stratabound mineral deposits
are closely linked to these structures, and these "faucets"
represent fundamental controls over brine and oil migration in
ancient sedimentary basins. The importance of fluid-expulsion
structures in exploration for stratabound mineral deposits has not
been recognized by the mineral exploration industry; the genetic
link to fluid-migration pathways is not understood by the
exploration industry, and in the past, these structures have been
misidentified and misinterpreted.
[0034] Expulsion of brine and oil from confined aquifers or through
seals in oil reservoirs profoundly alters fluid migration by
reducing dynamic fluid pressure, which can stop migration entirely.
Alternatively, oil can be trapped in fluid-expulsion structures or
in permeable rocks adjacent to the expulsion structure.
Fluid-expulsion structures have been misidentified as "collapse"
pipes, "cryptovolcanic" and "cryptoexplosive" structures,
astroblemes, meteorite impact structures, and karst breccias.
Misidentification of fluid-expulsion structures masked the true
role of these structures in migration of metal-bearing, basinal
fluids and hydrocarbons. This new frontier in exploration is
two-fold: (1) Fluid-expulsion structures can indicate the location
of potential stratabound mineral deposits; and, (2) Fluid-expulsion
structures can trap migrating oil, or the pressure release can
terminate oil migration. Fluid-expulsion structures occur in most
sedimentary basins that produced hydrocarbons. The link between
fluid migration and expulsion structures is not part of the
knowledge of the mineral exploration industry, and oil companies
focus mainly on detecting seal ruptures in reservoirs rather than
using ancient fluid-expulsion structures as keys to the dynamic
behavior of fluids in ancient sedimentary basins.
[0035] Ancient fluid-expulsion structures can be identified in the
geologic record. These features controlled distribution of
stratabound mineral deposits and affected the dynamic behavior of
migrating brine and oil. These structures are widely distributed in
Phanerozoic oil-producing basins, but these structures are
localized in clusters leaving large areas of sedimentary basins
devoid of fluid-expulsion features.
[0036] A corollary to the relationship between fluid-expulsion
structures and stratabound mineral deposits is that fluid-expulsion
structures exert fundamental control on hydrocarbon migration, and
identification of these structures is an important tool to
understand where hydrocarbon reservoirs are not likely to occur, as
well as to identify places where secondary reservoirs were
created.
[0037] With regard to stratabound mineral deposits, a snapshot of
three areas (FIG. 1) in the U.S. where fluid-expulsion structures
are related to stratabound mineral occurrences can be seen. Many of
these were mines. These examples illustrate the extraordinary
global exploration opportunity presented by the concepts described
herein. The three regions addressed as examples are: (1)
Northwestern Arizona in the Grand Canyon region, also known as the
Arizona Strip; (2) The San Rafael Swell in east-central Utah; and,
(3) Mid-Continent region where southern Illinois, Indiana, Ohio,
and western Kentucky adjoin. These areas were selected because
rocks and structures have been described adequately in the
literature, and because each region shows important variations in
composition and physical characteristics of fluid-expulsion
structures. All of these fluid-expulsion features described in
these snapshots contain hydrocarbons (asphalt) in breccia or in
cavities, which indicates that the brine contained liquid
petroleum. Fluid-expulsion structures in each of these areas
contain mineral deposits in breccia or in stratabound hosts
adjacent to fluid-expulsion structures or dikes. The mineral
deposits vary greatly in contained metals, but the most common
metals are uranium, vanadium, copper, silver, gold, platinum group
metals, lead, zinc, and cobalt. Mines in northwestern Arizona have
produced uranium and vanadium, but copper, silver, gold, lead, and
zinc have also been mined. The San Rafael Swell has produced
substantial uranium and vanadium, and strata may host multi-metal
deposits that include copper, silver, gold, and platinum-group
metals. In the Mid-Continent region, fluorspar ore was a main
product of mines in the Hicks Dome area and in the Cave-In-Rock
mining district in southeastern Illinois, but galena and sphalerite
enhanced the value of the ore. A circular brecciated structure in
southern Ohio, named Serpent Mound, contains sphalerite, barite,
chalcopyrite, marcasite, and pyrite in a dolomite breccia. The
resource has not been exploited because it was judged too low in
grade by Cominco, based on three shallow drill holes.
[0038] These concepts can be applied to hydrocarbon exploration, so
a brief explanation is offered regarding relations between
fluid-expulsion structures and oil and gas exploration. There is a
systemic couple between formation of metal-bearing brine and
hydrocarbons because brine and hydrocarbons originate from the same
source rocks and share the same temperature ranges in subsiding
sedimentary basins. Of the numerous probable fluid-expulsion
structures that contain oil and gas, the Ames structure in Oklahoma
was chosen because it contains productive oil fields, and it has
been misidentified as an impact structure. Many other probable
fluid-expulsion structures have been misidentified as impact
structures so reevaluation of the origin of the Red Wing and
Newporte fields in North Dakota, Cass County and Warren in
Michigan, and the Lima field in Indiana is in order. Reserves in
these fields range between 10 and 700 MMBO. Although not all of
these oil fields will eventually be proved to be fluid-expulsion
structures, most are likely to be related to upward brine and oil
expulsion through seal ruptures in confined aquifers or hydrocarbon
reservoirs, which is not destructive to hydrocarbons as are
meteorite impacts.
[0039] FIG. 1 is an Index map showing three areas in the U.S. that
contain prominent fluids-expulsion structures. 1. Northwestern
Arizona in the Grand Canyon region. 2. San Rafael Swell in
east-central Utah. 3. Mid-Continent area in the vicinity of Serpent
Mound, Ohio.
[0040] Application of this site discovery technique to stratabound
mineral exploration programs will give a strong advantage over
competitors in pursuit of shallow, large, stratabound mineral
deposits that commonly contain uranium-vanadium, copper-silver,
gold-platinum group metals, lead, or zinc. Many of these
stratabound mineral deposits are multi-metal deposits that contain
valuable trace elements. The global scale to which this concept can
be applied derives from the association of oil-producing basins
with stratabound mineral deposits. All sedimentary basins that
contain hydrocarbon reservoirs had brine-, oil-, and gas-migration
pathways through which fluids moved from organic, metal-bearing
source beds to containment reservoirs or to aquifers and
fluid-expulsion structures. Without an exit into permeable beds or
into subsea vents (the "faucet"), fluids contained in pore spaces
in sedimentary rocks cannot migrate. Therefore, identification of
ancient fluid-expulsion structures provides a quick and inexpensive
way to identify likely locations at which warm, reduced brines
chemically reacted with lower temperature, oxidized formation fluid
to produce stratabound mineral deposits.
[0041] Use of this concept in hydrocarbon exploration will provide
a competitive advantage to any company by using satellite images to
locate the most highly prospective areas in a sedimentary basin
that could have formed reservoirs in highly permeable breccia, or
to locate the "faucet" that may have been instrumental in stopping
oil or gas migration in structural compartments. Use of this
concept to understand the dynamics of hydrocarbon migration and
entrapment is global in scope. Two types of traps are common in
fluid-expulsion structures: (1) Cap-rock over porous,
hydrocarbon-filled breccia; and, (2) Stratigraphic traps adjacent
to the expulsion structure in which hydrocarbons invaded permeable
aquifers below seals.
[0042] In subsiding sedimentary basins, metal-bearing, carbonaceous
shale and siltstone descend into increasingly higher temperature
regimes during which water is expelled from fine-grained clastic
and carbonate sediment as part of the lithification process.
Diagenetic changes in the sediment reflect changes in the chemical
composition of pore water, increased temperature, and dewatering of
clay minerals. In general, salinity increases with increasing
burial depth, which increases chlorine concentration to permit
inorganic, metallic coordination compounds to form as metals leach
into the chemically reduced brine. Because organic compounds mature
with increasing burial, metal-bearing, warm, saline brines are
closely associated with oil and gas generation. Organic
coordination compounds begin to form early in the burial sequence
at temperatures as low as 25.degree. C. Carboxylic and naphthenic
acids, porphyrins, and asphaltenes combine with metals in
chemically reduced brine and transport the metals in the brine
plume. Dissolution of evaporites in the stratigraphic sequence can
greatly increase salinity of the pore fluid above the normal
salinity increase caused by membrane filtering, and higher
concentrations of chlorine in brine increases the concentration of
metal-chloride coordination compounds. Metals are leached from
organic-rich source rocks into the warm, acidic brine in an orderly
progression determined by the thermochemical properties of metals
in different valence states, and this progression is summarized by
metal-maturity windows. These organic-rich source rocks begin to
produce gas and oil under increasing temperature and dynamic
pressure, and metal-bearing brine enters permeable rock units
before gas and oil enters the same permeable rock units. Metals
that enter the brine at lower temperatures and lower salinity
migrate with the first brines into aquifers, whereas metals that
enter the brine at high temperatures and high salinity in the
"hydrocarbon kitchen" are the last metals to migrate with oil. The
last dewatering event is expulsion of "metamorphic water" from the
source rock, which is the highest temperature metal-leaching event
that affects only the deeply buried parts of the basin. The orderly
progression of metal leaching from the source rock yields a
conveyor belt of different metals carried in moving brine and,
ultimately, leads to partitioning of metals in sedimentary
basins.
[0043] Tectonic Settings of Basins
[0044] On the scale of a sedimentary basin, the tectonic setting is
a determining factor of eventual burial depth, and the final burial
depth influences the sequence of metals released into chemically
reduced brine (FIG. 2). Heat and dynamic pressure force brines,
oil, and gas to migrate into permeable strata within the basin,
migrate to permeable transfer zones such as faults, or break
confining seals in brine and hydrocarbon reservoirs. Generally,
brine and hydrocarbons are expelled up-dip toward basin edges. A
basin that is not buried deeply may not generate enough heat during
burial to leach a complete range of metals from source rocks or to
produce mature hydrocarbons, so some basins may have generated and
precipitated metals from low-temperature maturity windows and
biogenic gas probably would have been the principal hydrocarbon.
Other basins, such as basins with overthrust margins, may bury
sediment deeply, and high temperatures of deep burial can promote
leaching of a wide range of metals into the acid, reduced, warm
brine, as well as creating mature hydrocarbons. Extreme dynamic
pressure can force brines to break reservoir seals, which will move
metals to places of chemical and thermal disequilibrium where
stratabound mineral deposits are precipitated, and permit oil to
migrate into upper levels of the sediment stack through expulsion
breccias.
[0045] FIG. 2 is a schematic rendition that shows four examples of
the role of tectonic control of sediment burial and metal transport
in sedimentary basins. A--Shallow burial of a relatively thin
sedimentary sequence leached Au, Cu, Ag, U, and V from source
rocks. B--Deeper burial of source rocks produced the characteristic
leaching sequence of U, V, Cu, Ag, and Au at lower temperatures and
Pb and Zn at temperatures of oil generation. C--A thin sedimentary
sequence buried by overthrusts first releases low-temperature
metals from source rocks and Pb and Zn are leached at oil
generation temperatures. A strong directional component to dynamic
pressure and brine migration direction characterizes this scenario.
D--A thick sedimentary sequence buried by overthrusts releases the
typical sequence of metals from source rocks, and metamorphic water
carrying Au and Cu is expelled from most deeply buried sediment. A
strong directional component to dynamic pressure and
brine-migration direction characterizes this scenario.
Metal-Maturity Windows
[0046] The concept of metal-maturity windows is based on prograde
thermal maturation of source rocks during progressive burial, and
this concept can be used to predict the principal metal
associations in stratabound mineral deposits. The sequence of metal
leaching from a source rock into saline, reduced brine is
predictable. Metals leach from source sediment, most commonly black
shale, in a specific sequence determined by physical and chemical
characteristics of the sediment and brine, and by thermochemical
behavior of elements and coordination compounds. Metals form
coordination compounds in a predictable sequence during increasing
temperature, and this sequence is summarized by "metal-maturity
windows". The five "metal-maturity" windows are a preliminary
summary of probable temperature ranges at which maximum leaching
and maximum degree of association of coordination compounds is
expected. Metal-maturity windows integrate published temperature
and composition data of fluid inclusions from mineral deposits,
mineral-stability conditions, and calculations of thermodynamic
maximum degree of association for inorganic coordination compounds.
Interpretation of fluid-inclusion data does not account for higher
temperatures recorded by fluid inclusions that result from
universal exothermal chemical reactions of metallic mineral
precipitation. The temperature ranges for the windows are
approximate. Each window is identified by the most common metals
that dissolve into the reduced brine in a particular temperature
range, but other metals, such as Co, Ni, La, Cr, Mo, and rare earth
elements can be substantial metallic components of some
windows.
TABLE-US-00001 Metal-Maturity Windows U--V--(Th) Window: 35.degree.
C. to 100.degree. C. Au--Pt--Pd Window: 60.degree. C. to
110.degree. C. Cu--Ag--(Ba) Window: 60.degree. C. to 120.degree. C.
Pb--Zn--Ba Window: 70.degree. C. to 180.degree. C. Au--Co--Cu
Window: 175.degree. C. to 275.degree. C.
[0047] In every subsiding sedimentary basin, the interactions among
burial depth, temperature increase, dewatering of sediment,
hydrocarbon maturity, metal-maturity windows, brine expulsion and
migration, and metallic-mineral precipitation are universal (FIG.
3). The physical and chemical principles that interact during
subsidence of a basin produce similar predictable results that can
be modeled to reconstruct fluid-flow pathways and estimate
locations that are most likely to contain specific types of
metallic mineral deposits. The principal variable among different
basins is the metallic composition of source rocks in the subsiding
basin, which determines which metals are deposited eventually at
chemical oxidation-and-reduction reaction (redox) sites. The
evolving brine changes metal composition over millions of years.
The earliest portion of the metal-bearing brine at the lowest
temperature metal-maturity window will be forced by heat and
pressure from the original site of metal dissolution. The brine is,
in effect, a moving conveyor belt of different brine compositions
and metal components, and this conveyor belt can be tapped at any
weakness in host aquitards to force brine upward to shallow depths
where thermal and chemical disequilibrium precipitate metallic
minerals. The brines at the lowest temperature and lower salinities
may extend farthest from the source rock in the "hydrocarbon
kitchen", and these brines may be able to exploit the first
weaknesses in seals of evolving oil and gas reservoirs. The types
of weaknesses that can be exploited in evolving reservoirs are
faults, fracture systems at anticlinal crests, injected sand
bodies, mud diapirs, salt diapirs, or gas chimneys. These vents can
expel metal-bearing brine, oil, gas, and commonly a mixture of all
three from deeper parts of the sedimentary basin into shallow
sediment. Venting of brine and oil may result in reduction of
dynamic pressure, which may stop oil and brine migration.
[0048] The combination of metal-maturity windows with migration
patterns of brine and oil in a sedimentary basin aids predictions
about where stratabound mineral deposits might occur, the metal
associations that might result, and potential locations of
secondary oil and gas reservoirs.
[0049] Hydrocarbon Maturity
[0050] Generation of hydrocarbons and leaching of metals into warm,
saline brine occur through the same temperature range, and
metal-bearing brine and oil are closely linked. Organic carbon is
the most concentrated in deep-marine sediment deposited between
2,000 and 6,000 ft (about 610 and 1,830 m) and lesser amounts of
organic carbon occur in brackish and shallow, continental-shelf
environments. Rocks classed as "good source rocks" commonly have
between 1% and 10% organic carbon, most of which is contained in
"kerogen", which is a complex polymeric mixture. In subsiding
sedimentary basins dominated by marine sediment, biogenic gas forms
in the upper 3000 ft (about 920 m) in at temperatures less than
about 60.degree. C. Between about 60.degree. C. and 150.degree. C.,
heat splits chemical bonds of organic matter to form Type I or Type
II kerogen, and liquid petroleum and thermogenic gas are generated
in the "oil window". Mature hydrocarbons are generated in the same
temperature range in which metals are leached from the source rocks
that generated oil (FIG. 3). Not only is chlorine available to form
coordination compounds, but organic acids, light paraffins,
asphaltenes, and porphyrins, are available to form organic
coordination compounds that bond with leached metals. Insolubility
of brine and petroleum fractionates the two fluids. Viscosity
differences and differences in molecular radii between brine and
hydrocarbons may permit the metal-bearing brine to migrate from
source rocks before liquid petroleum leaves the source rock, when
dynamic pressure from tectonic activity and differential thermal
diffusion force fluids from the source rock. Invasion of liquid
petroleum into aquifers probably follows the initial migration of
metal-bearing brine into aquifers. Anticlinal, fault, and
stratigraphic traps can confine both fluids. Although brines may be
able to exploit the first weaknesses in reservoir seals, oil may
follow brine into new traps high in the fluid-expulsion structure.
Faults, fracture systems at anticlinal crests, injected sand
bodies, mud diapirs, salt diapirs, and gas chimneys form the
"faucets" that allow metal-bearing brine, oil, gas, and commonly a
mixture of all three, to migrate upward into shallow secondary
traps from deep in the sedimentary basin.
[0051] In FIG. 3, general relations are shown among burial depth of
sediment, temperature increase during progressive burial, pressure
increase during continuing burial, dewatering periods caused by
increasing pressure and temperature, hydrocarbon maturity, and
metal-maturity windows. Metal-maturity windows are based on
temperature stability ranges of coordination compounds and
fluid-inclusion data that records temperature of crystallization of
metallic compounds. Hydrocarbon generation is closely related to
dissolution of metals into reduced, warm brine. Expulsion of
metal-bearing brine and hydrocarbons from sedimentary basins are
different phases of the same thermal system.
[0052] Subsea Fluid-Expulsion Structures
[0053] Modern counterparts of ancient fluid-expulsion structures
are recorded on seismic profiles from hydrocarbon producing, subsea
basins. Hydrocarbons and brine plumes that are under high dynamic
pressure can exploit weaknesses in reservoir seals, such as faults
and fractures, or can intrude permeable sand injectites that break
upward through young sediment layers. Pore-fluid pressure in the
Popeye-Genesis mini-basin (Gulf of Mexico) hydraulically fractured
overlying shale seals, which allowed upward fluid migration; fluids
vented to the seafloor to form mud volcanoes where gas hydrates
formed. Recently, a study of "seal-bypass systems" by Cartwright
and others (2007) has focused on seismic criteria to identify
mechanisms by which hydrocarbons bypass and breach reservoirs. Seal
bypass systems consist of fault bypass, intrusive bypass (igneous
intrusions, sand intrusions, and mud diapirs and diatremes, and
salt diapirs), and pipe bypass (dissolution pipes, hydrothermal
pipes, blowout pipes, and seepage pipes). Although analysis of
these bypass systems by Cartwright and others focused on
hydrocarbon migration, saline, metal-bearing brines are part of the
same migration systems as hydrocarbons.
[0054] Intrusive-bypass systems are caused by sandstone intrusions,
igneous intrusions, mud diapirs, and diatremes. Sandstone
intrusions result from high fluid pressures in the basin. Sand
injection occurs as a fluidized mass that has flow velocities on
the order of 1 to 2 cm/s.sup.-1. In the United Kingdom Atlantic
margin petroleum province, sand injectites have penetrated
vertically 3,300 ft (1,000 m) above the parent sand body across
competent sealing sequences. Sandstone intrusions (FIG. 4) can
remain as highly permeable pipes for many millions of years until
pore space is occluded or until the high fluid pressure is
dissipated. Pore-space occlusion may occur by diagenetic processes
that include precipitation of metallic minerals in the pipe or as
replacement stratabound deposits in permeable beds that border the
pipe. When high fluid pressure is dissipated neither brine nor oil
can migrate. Igneous intrusions can cause intense brecciation of
host rock and the intrusive body (FIG. 5). Fractures at the
metamorphic contact can provide long-term conduits, which may fill
with metallic minerals in veins. Injection of magma into wet,
non-consolidated sediment can greatly alter the metallic signature
of minerals precipitated in pipes or as stratabound deposits; an
ultramafic magma would produce different metallic minerals and
trace metals than a rhyolitic magma. Mud diapirs and diatremes form
when fine-grained, clay-rich sediment liquefies and fails; upward
injection is likely to be episodic. Upward migration of fluids is
episodic as well, and flow volumes are small. Therefore, mud
diapirs and diatremes are not likely to be centers of large-scale
mineralization. Salt diapirs commonly fold and deform
non-consolidated sediment and deformation can severely modify
fluid-migration regimes and seal integrity. Fluid leakage near salt
diapirs occurs by complex fracture networks developed near the
contact between salt and host sediment. Fault and fracture systems
adjacent to salt diapirs are open for short periods, and are not
likely to vent large volumes of brine or hydrocarbons.
[0055] FIG. 4 shows a seismic profile of large-scale,
interconnected sand injectites, offshore United Kingdom, in the
Faeroe-Shetland Basin. Sand intrusions cross a low-permeability
sealing sequence of mudstone rendering the seal ineffective. The
submarine-fan reservoir, marked at the top by TF, was breached,
which permitted brine and hydrocarbons to migrate upward through
the sand injectite.
[0056] FIG. 5 shows a seismic profile of igneous sills intruded
into a clastic sequence offshore United Kingdom, Rockall Basin.
Sills are interconnected, high-amplitude bodies. Note that sills
appear to be breached by a fluid-expulsion structure or sand
injectite on the right side of seismic profile on both sides of the
word "sill".
[0057] Cartwright and others summarized "Pipe-bypass" systems and
separated dissolution pipes, hydrothermal pipes, blowout pipes, and
seepage pipes as the principal categories. In general, pipes are
the least-well documented features of seal-bypass systems, and are
defined as "seismically detected columnar zones of disturbed
reflections that may or may not be associated with subvertically
stacked amplitude anomalies." Pipes are commonly circular or
subcircular in plan-form, and are easiest to identify in 3-D,
horizon-based attributes. Dissolution pipes form in evaporite or
carbonate karst terrains where the high-quality evaporite seal is
pierced by dissolution so brine and oil can migrate upward through
overburden creating and expanding the cavity (FIG. 6). The greatest
potential for brine and oil expulsion probably occurs during pipe
formation, but once formed these pipes can remain centers of
fluid-expulsion for long periods. Hydrothermal pipes are related to
igneous intrusions where hydrothermal fluid is derived from magma
devolitilization and heating pore fluids. The composition and
volume of fluid created depends on magma composition, temperature,
intrusive volume, and permeability and composition of host
sediment. The mineral and trace metal suite produced by
hydrothermal fluids varies according to the composition of the
magma and host sediment. Hydrothermal pipes can reach heights of
1.8 ml (2.5 km). On seismic profiles, blowout pipes are columnar
zones of disturbed reflections or vertically stacked amplitude
anomalies (FIG. 7). The circular structure of blowout pipes is
common to all diatremes and has been explained as a means to
minimize energy loss caused by wall friction at the contact between
the upward moving fluidized injection and the host sediment. The
volume of fluid expelled is likely to be the greatest at the time
of formation, but some pipes show evidence of episodic flow.
Blowout pipes are limited to fine-grained sealing sequences.
Permeability may be retained in the pipe for millions of years,
allowing saline, metal-bearing brine and oil to stream upward
across a seal. Pockmarks at the top of the structures result from
strata that dip inward. Although Cartwright and others did not
address the texture of material in the pipe, they cited granular
particles in a fluidized system, and this material is most likely
to form breccia and breccia dikes that are so common in ancient
fluid-expulsion structures. Seepage pipes are recognized in seismic
profiles as columnar zones of disrupted reflections with localized
amplitude anomalies (FIG. 8). Seepage pipes appear to occur mainly
in sand or silt-dominated sequences where fluids bleed off into
permeable host sediment.
[0058] FIG. 6 shows a seismic profile across three dissolution
pipes in the eastern Mediterranean Levant Basin. The regional seal
is the Messinian evaporite sequence (ME), which has been dissolved
below three vertical collapse pipes (labeled 1, 2, and 3). These
pipes broke the evaporite seal and permitted fluid migration across
the regional seal.
[0059] FIG. 7 shows a seismic profile of a blowout pipe from
offshore Namibia. Vertically stacked pockmarks record a long period
of upward fluid migration in the pipe.
[0060] FIG. 8 shows a seismic profile of a seepage pipe at the
arrow (offshore Scotland in the Faeroe-Shetland Basin). This pipe
originated from the crest of a small fold on the top surface of an
aquifer. The absence of pockmarks suggests a slow rate of upward
brine, oil, or gas migration from the aquifer.
[0061] Predicting Locations of Fluid-Expulsion Structures
[0062] Fluid-expulsion structures occur in sedimentary basins in
predictable locations that are controlled by a combination of
preexisting regional structures, faults and folds in the
sedimentary basin, and regional geometry of sedimentary units in
the sedimentary basin. Predicting locations of fluid-expulsion
structures is difficult to quantify for all sedimentary basins
because sedimentary fill, tectonic evolution, and structural
settings are different for each basin. However, geologic map
analysis can narrow the region in which expulsion structures can be
expected to have formed.
[0063] Brine- and oil-expulsion structures are commonly preserved
in strata deposited on stable continental shelves near the
continental slope break. Pipes form distant from the deepest and
most quickly subsiding part of the sedimentary basin where
temperatures are highest and metals are leached from organic shale
and siltstone. Metal-bearing brines and hydrocarbons are pumped to
the edges of the subsiding sedimentary basin where preexisting
geologic features, such as basement arches and faults, represent
zones of weakness in seals or form barriers to migration of
overpressured brine and hydrocarbons. In the U.S., structures such
as the San Rafael Swell, Utah, Cincinnati Arch, Ohio, Nashville
Dome, Tennessee, and Nemaha Arch, Oklahoma, are the types of
regional structures that may have localized fluid-expulsion
structures in crestal regions or on the flanks of these uplifts.
Faults and folds, including basement structures, that occur in the
path of migrating metal-bearing brines and hydrocarbons on the thin
edges of subsiding sedimentary basins are ideal places for upward
migration of metal-bearing brine and oil. The Lisbon Valley
stratabound copper deposits are classic examples in which
hydrocarbon-bearing, metal-rich, warm, reduced, acid brine and
minor oil migrated upward along a fault near the crest of the
Lisbon Valley Anticline, and vented into aquifers of the Burro
Canyon and Dakota Formations (Cretaceous) that now contain
stratabound copper deposits (Hahn and Thorson, 2006). Flanks and
crests of anticlines are predictable locations for brine- and
oil-expulsion expulsion features where tension fractures may
provide weaknesses that can be exploited by overpressured brine and
oil plumes. The regional geometry of sedimentary units in a
subsiding sedimentary basin may cause fluid-expulsion structures to
localize over the flexure that marks the transition from
shallow-marine deposits to shelf sediment, as in the Anadarko
basin, Oklahoma. In the Mid-Continent, that flexure in the
Appalachian Basin may have produced numerous features. Finally, at
places where aquifers thin between aquitards against regional
arches or anticlinal folds, overpressured fluid may break seals and
be injected upward forming linear zones of pipes or dikes along the
flanks of the fold.
[0064] As can be seen by the flowcharts in FIGS. 9, 10A, 10B, 11,
12A, and 12B, a variety of methods can be utilized to practice
embodiments of the invention. Referring first to flowchart 900 a
method of targeting a location for mineral deposit exploration can
be seen. In block 904, a computer is used to obtain an image of an
area of land. The image is used to determine at least one
fluid-expulsion structure present on the land, as shown by block
908. Based on this determination, an area proximate the
fluid-expulsion structure can be designated as a mineral
exploration location, i.e., a targeted location.
[0065] FIGS. 10A and 10B illustrate a more detailed example of a
method of targeting a location for mineral exploration in flowchart
1000. In block 1004, an image of an area of land can be obtained.
Blocks 1008, 1012, and 1016 offer three examples of how such an
image could be obtained. For example, block 1008 illustrates that a
satellite image of an area of land could be obtained. Thus, for
example, satellite images from commercial satellite services could
be utilized. One example of a commercial satellite service is
Google. Block 1012 shows that an aerial photograph of an area of
land could be obtained. In some instances, the resolution of the
image of the land area may be insufficient to determine enough
detail. In such instances, a higher resolution image may be
obtained. For example, block 1016 shows an example in which a
ground sample distance resolution of 20 meters could be obtained.
As another example, a ground sample distance resolution of 5 meters
could be obtained, as shown by block 1020.
[0066] The image can then be transmitted to a computer for use by
an analyst or pattern recognition software program. Thus, block
1024 illustrates that the image can be reviewed so as to determine
if at least one fluid-expulsion structure is present. As explained
herein, fluid-expulsion structures have been shown by the inventor
to be indicators of the presence of mineral deposits worthy of
production. The method of determining the presence of a
fluid-expulsion structure may be performed by an individual analyst
or it may be performed through the use of software programmed to
search for at least one physical pattern on the image. Block 1028
illustrates that a fluid-expulsion structure in the form of a
breccia pipe can be searched for. Similarly, block 1032 illustrates
that a fluid-expulsion structure in the shape of a sand injectite
can be searched for. In addition, one may search for multiple
fluid-expulsion structures. Thus, one may direct the search for a
cluster of fluid-expulsion structures found on the image, for
example, as shown by block 1036.
[0067] Once a fluid-expulsion structure is located on the image,
the area proximate to that fluid-expulsion structure may be
designated as an exploration location. This is shown by block 1040.
As one example, one can target the area within the fluid-expulsion
structure itself for mineral exploration, as shown by block
1044.
[0068] A deposit-type approach may also be conducted for a selected
site. This can be accomplished, as shown by block 1048, by
utilizing metal-maturity windows to select a range of metal
compositions desired in a mineral deposit.
[0069] Referring now to FIG. 11, a flowchart 1100 demonstrating a
method of locating a hydrocarbon reservoir can be seen. In block
1104, a computer image of an area of land can be obtained. In block
1108 a determination can be made from the image of at least one
fluid-expulsion structure being present on the land. In block 1112,
an area proximate to, or on, the fluid-expulsion structure can be
designated as a hydrocarbon exploration location.
[0070] FIGS. 12A and 12B illustrate a more detailed example of a
method of targeting sites for further hydrocarbon exploration. In
flowchart 1200, a computer image can be obtained of an area of
land, as shown in block 1204. As noted above, the computer image
can be generated from a satellite image as shown in block 1208 or
via an aerial photograph as shown in block 1212. The image can be
obtained with the necessary resolution to determine land features.
For example, block 1216 shows an example of an image obtained with
a ground sample distance resolution of less than 20 meters. Block
1220 shows an example of using an image with a ground sample
distance resolution of less than 5 meters. One might choose to use
smaller resolutions, as desired. The image can be transmitted
across a network to a site used by an exploration company. Thus,
one might use a digital image of the land site and transmit it
across a digital network for use or display on an exploration
company's computer. Or, for example, one might purchase a file of
multiple images and store that file on a computer memory for use in
the target analysis process.
[0071] In block 1224 of flowchart 1200, a determination can be made
as to whether a fluid-expulsion structure is present on the image.
This determination could be made by a human analyst or by a
software program configured to search for a pattern on the image.
Block 1228 illustrates that the image could be searched for a
breccia pipe. Block 1232 illustrates that the image could be
searched for a sand injectite. And, block 1236 illustrates that the
image could be searched for more than one fluid-expulsion
structure. For example, a cluster of fluid-expulsion structures
could be searched for.
[0072] Based on the results of the image evaluation, an area of
land on the image may be targeted. For example, an area proximate
to the fluid-expulsion structure could be designated as a
hydrocarbon exploration location, as shown in block 1240. As noted
above, hydrocarbons may utilize voids in the strata around the
fluid expulsion structure to migrate. Thus, the targeted location
for development can be further targeted to strata proximate to the
fluid expulsion structure, as shown by block 1244. Moreover, one
may estimate the time of hydrocarbon generation and determine a
migration direction in order to determine a historical progression
of the hydrocarbon fluids through aquifers. This can then be used
to establish which fluid expulsion structures among a plurality of
fluid expulsion structures are most likely to contain hydrocarbons,
as shown by block 1248.
[0073] Referring now to FIG. 13, an example of a system for
obtaining satellite images can be seen. In FIG. 13, a satellite
1304 takes a satellite image of an area of land. The image is
transmitted to a receiver 1308 which in turn transmits the image
across a computer network to computer 1312. From computer 1312, the
image can be analyzed or transmitted further to yet another
computer and across a second computer network.
[0074] FIG. 14 illustrates a block diagram of a device that can be
used for the computer in FIG. 13 as well as the other computerized
devices described herein. System 1400 is shown comprised of
hardware elements that are electrically coupled via bus 1408,
including a processor 1401, input device 1402, output device 1403,
storage device 1404, computer-readable storage media reader 1405a,
communications system 1406 processing acceleration (e.g., DSP or
special-purpose processors) 1407 and memory 1409. Computer-readable
storage media reader 1405a is further coupled to computer-readable
storage media 1405b, the combination comprehensively representing
remote, local, fixed and/or removable storage devices plus storage
media, memory, etc. for temporarily and/or more permanently
containing computer-readable information, which can include storage
device 1404, memory 1409 and/or any other such accessible system
1400 resource. System 1400 also comprises software elements (shown
as being currently located within working memory 1491) including an
operating system 1492 and other code 1493, such as programs,
applets, data and the like.
[0075] System 1400 has extensive flexibility and configurability.
Thus, for example, a single architecture might be utilized to
implement one or more servers that can be further configured in
accordance with currently desirable protocols, protocol variations,
extensions, etc. However, it will be apparent to those skilled in
the art that embodiments may well be utilized in accordance with
more specific application requirements. For example, one or more
system elements might be implemented as sub-elements within a
system 1400 component (e.g. within communications system 1406).
Customized hardware might also be utilized and/or particular
elements might be implemented in hardware, software (including
so-called "portable software," such as applets) or both. Further,
while connection to other computing devices such as network
input/output devices (not shown) may be employed, it is to be
understood that wired, wireless, modem and/or other connection or
connections to other computing devices might also be utilized.
Distributed processing, multiple site viewing, information
forwarding, collaboration, remote information retrieval and
merging, and related capabilities are each contemplated. Operating
system utilization will also vary depending on the particular host
devices and/or process types (e.g. computer, appliance, portable
device, etc.) Not all system 1400 components will necessarily be
required in all cases.
CONCLUSIONS
[0076] The three examples discussed above illustrate that new
stratabound exploration targets can be generated in areas that have
been overlooked and that interest can be rekindled in abandoned
mining districts, and target hydrocarbon reservoirs. Screening for
ancient fluid-expulsion structures is a quick and inexpensive
method to locate specific places where chemical reactions between
expelled reduced brine and oxidized host rocks are expected to form
stratabound mineral deposits. The same processes that force brines
to break seals and migrate upward also apply to upward migration of
oil and gas into higher reservoirs. The exploration concepts
outlined in this patent are an extremely powerful, and
time-efficient way to locate mineral and hydrocarbon exploration
targets. The concepts outlined in this patent are not believed to
be part of exploration knowledge of the mineral or oil industries.
Thus, it provides a competitive advantage in exploration.
[0077] These concepts are global in scope. Fluid-expulsion
structures or linear expulsion bands should occur in all
oil-producing, sedimentary basins. Cartwright and others (2007)
demonstrated conclusively that seal ruptures in hydrocarbon
reservoirs are common events in modern subsea sedimentary basins.
Therefore, Neoproterozoic and Phanerozoic sedimentary basins are
possible places to explore. Using these concepts, decisions about
where to explore to the greatest advantage is a simple and quick
process that employs data commonly available to the public. For
most oil-producing basins, information in the public domain
describes burial histories and timing of gas and oil generation.
This information can be integrated with the metal-maturity window
concept and with information on brine-oil migration pathways to
gain a more precise understanding of probable locations of
stratabound mineral deposits and hydrocarbon reservoirs.
[0078] Screening for fluid-expulsion structures will not be equally
effective everywhere because ground cover can obscure surface
indications of structures and breccia intrusions on satellite
images, and render remote exploration methods ineffective.
Vegetation can obscure surface features on the ground, so satellite
and photographic observations will be hampered in jungle terrain.
Glacial till, dune fields, and thick, intensely weathered mantles
can cover or destroy surface characteristics of circular features.
Air-borne geophysical methods might aid in locating circular
features, but much of the effectiveness of geophysical methods will
depend on thickness of glacial till, sand, or laterite.
[0079] Ground-based geophysical and geochemical surveys were used
in northwestern Arizona, and in the Mid-Continent these studies may
be useful precursors to drilling at circular structures. Surface
surveys of magnetic signatures, AMT results, and gravity profiles
may be useful tools to locate drill targets for mineral deposits.
Soil geochemical surveys were shown to be effective for locating
potential mineralized breccia pipes in northwestern Arizona. Helium
soil-gas surveys have shown mixed success as an exploration tool in
northwestern Arizona, and although radon soil-gas surveys were not
used, they may be effective tools. Interpretation of seismic
profiles may detect vertical pipes of breccia that record ruptured
reservoir seals where seismic patterns of layered strata are
jumbled. Stream-sediment surveys may provide local geochemical data
important to locating mineral deposits near or in fluid-expulsion
structures. Not all geophysical and geochemical survey methods will
be useful in all geologic and geographic settings, and different
methods will have to be matched to specific problems.
[0080] The quality of satellite and photographic images used to
locate ancient fluid-expulsion structures facilitates improved
results. In some areas, satellite images, such as Google Earth
images, are of poor quality and little can be seen on the surface.
In other areas, such as northwestern Arizona, the circular pipes
are too small to be seen on Google images. Images from NASA World
Wind are based on 30 m pixels, and they are generally too coarse to
detect circular features on the scale of fluid-expulsion
structures. High-resolution satellite images are available by
subscription, and these could be very useful. For the most part,
currently available Google images (provided at www.google.com) are
satisfactory at the current scale used for exploration.
[0081] Fluid-expulsion structures can be characterized by the
following features:
[0082] Fluid-expulsion structures occur in most oil-producing
sedimentary basins.
[0083] Fluid-expulsion structures occur in clusters.
[0084] Fluid-expulsion structures are generally circular, oval, or
subcircular in shape.
[0085] Fluid-expulsion structures can be linear dikes, vermiform,
or lenticular structures.
[0086] The outer rim is generally uplifted, with an internal moat,
and a central uplift. Annular rings are common, and the rings can
be fault bounded.
[0087] Breccia and randomly oriented blocks of sedimentary rock
occur throughout the structure.
[0088] Breccias are commonly sedimentary rock fragments in a finely
ground matrix of sedimentary rock debris. Some structures contain
igneous rock clasts and some matrix can form from finely comminuted
igneous material.
[0089] Breccia, clasts, and matrix are chemically reduced.
[0090] Bitumen, asphalt, or liquid hydrocarbons occur in breccia
and in permeable host rocks.
[0091] Permeable host strata that are penetrated by sedimentary
intrusive breccia are reduced.
[0092] Fluid-expulsion structures and permeable host rocks contain
sulfide minerals and hydrocarbons.
[0093] Magnetic low anomalies occur over fluid-expulsion structures
because magnetic minerals were chemically reduced.
[0094] Low gravity anomalies may characterize the less-dense
brecciated core of the structure.
[0095] AMT soundings may locate conductive zones of sulfide
minerals as stratabound deposits in host rocks or in the breccia
pipe, but AMT soundings are of no use to find hydrocarbons.
[0096] Chemical analyses of soil samples may show high anomalies of
Cu, As, Ag, Co, Cr, Hg, Mo, Ni, Pb, Zn, Sb, Sr, U, V, and P.
[0097] Rock exposed at the surface can contain oxidized Cu and Fe
minerals.
[0098] Shatter cones are absent, but diagenetically created
cone-in-cone structures may occur in carbonate rocks.
[0099] Coesite and shocked quartz are absent, although deformed
lamellae in quartz (PDFs) could superficially resemble shocked
quartz and have been inherited from protoliths.
[0100] "Glass" and fused silicate rocks are absent, but bitumen can
superficially resemble fused rock.
[0101] Authigenic quartz, saddle dolomite, rhombs of dolomite,
rhodochrosite, and calcite are common as late cement in
carbonate-rich breccia and host rocks.
[0102] Some fluid-expulsion structures are the focus of hydrocarbon
reservoirs.
[0103] The potential value of stratabound mineral deposits
associated with fluid-expulsion structures is immense in terms of
potential volume of metal and the great number of chemical elements
of commercial value that were transported in reduced brines. It has
been estimated that there is an undiscovered uranium endowment in
northwestern Arizona and adjacent Utah at 1,300,000 tons of
U.sub.3O.sub.8 in an area of 16,728 sq mi (about 43,493 sq km). On
the San Rafael Swell, the Temple Mountain mining district produced
1,287,000 lbs of U.sub.3O.sub.8 and 3,800,000 lbs of V.sub.2O.sub.5
between 1948 and 1956 (Bartsch-Winkler and others, 1990), and that
could represent only small amount of the uranium and vanadium that
existed before erosion. In the Mid-Continent region, the value of
stratabound mineral deposits associated with fluid-expulsion
structures cannot be estimated because production data are missing
from the Hicks Dome area, and the Serpent Mound area has not been
mined for MVT-type deposits. Metal endowment deposited from the
reduced brine produced in the Appalachian basin could include
uranium, vanadium, copper, and silver, but also could contain
significant gold, platinum, palladium, ruthenium, and other
platinum group metals in addition to lead and zinc. It is unlikely
that this range of endowed metals has been targeted in previous
exploration programs in the Mid-Continent region.
[0104] The potential value of hydrocarbon accumulations in
fluid-expulsion structures is immense. Estimated reserves of a few
oil fields, which are most likely associated with fluid-expulsion
structures, range between 10 MMBO to 700 MMBO, and at $40.00
USD/barrel would be worth 400 million USD and 280 billion USD.
Reservoirs in fluid-expulsion structures are generally shallow in
ancient sedimentary basins. Bore holes on land are much cheaper to
drill than drilling over deep marine oil reservoirs. Moreover, many
of these structures occur near well-developed infrastructures that
can support drilling projects. It is unlikely that oil and gas
reservoirs associated with fluid-expulsion structures have been
targeted by explorationists, although oil is produced from many
fluid-expulsion structures, exploration geologists have not made
the connection between fluid-expulsion structures and breaches of
reservoir seals in subsea basins.
[0105] Two types of targets exist in fluid-expulsion structures for
stratabound mineral deposits and for hydrocarbon reservoirs.
Stratabound mineral deposits in fluid-expulsion structures have
targets in: (1) Breccia pipes that were mineralized by upward
migrating, metal-bearing, warm, reduced brine where redox chemical
reactions precipitated mineral deposits; (2) Peripheral stratabound
mineral deposits in permeable rock units adjacent to the breccia
pipes where redox chemical reactions precipitated mineral deposits
in tabular form. Hydrocarbon resources in fluid-expulsion
structures have targets in: (1) Breccia pipes that had seals above
porous breccia into which hydrocarbons migrated; and (2) Reservoirs
peripheral to breccia pipes that were formed where hydrocarbons
migrated laterally into permeable rock units overlain by seals.
[0106] The exploration industry has not made the connection from
generation of oil and metal-bearing brine, to fluid migration and
fluid-expulsion structures, and to hydrocarbon traps near seal
ruptures and stratabound mineral deposits. Competition for
prospective land should be minimal outside areas with known
stratabound mineral production, and opportunities to secure land
positions to drill for hydrocarbons should be less costly using
these new concepts.
[0107] These concepts open new terrain to exploration programs that
the mineral and oil exploration industry currently ignores. That
many of the circular structures in the U.S. have been identified as
meteorite impact structures is a positive diversion because
"impacts" generate little exploration interest. Similarly, circular
structures that have been investigated as possible kimberlite pipes
are likely to be ignored with regard to stratabound and hydrocarbon
exploration because geophysical signatures of fluid-expulsion
structures are different from buried kimberlite bodies. Using
fluid-expulsion structures as a tool to target stratabound mineral
deposits and hydrocarbon reservoirs is not being applied by the
exploration industry. A company that has the vision to bring this
intellectual property to mineral- and hydrocarbon-exploration
programs has a clear competitive advantage.
[0108] While various embodiments of the invention have been
described as methods or apparatus for implementing the invention,
it should be understood that the invention can be implemented
through code coupled to a computer, e.g., code resident on a
computer or accessible by the computer. For example, software and
databases could be utilized to implement many of the methods
discussed above. Thus, in addition to embodiments where the
invention is accomplished by hardware, it is also noted that these
embodiments can be accomplished through the use of an article of
manufacture comprised of a computer usable medium having a computer
readable program code embodied therein, which causes the enablement
of the functions disclosed in this description. Therefore, it is
desired that embodiments of the invention also be considered
protected by this patent in their program code means as well.
Furthermore, the embodiments of the invention may be embodied as
code stored in a computer-readable memory of virtually any kind
including, without limitation, RAM, ROM, magnetic media, optical
media, or magneto-optical media. Even more generally, the
embodiments of the invention could be implemented in software, or
in hardware, or any combination thereof including, but not limited
to, software running on a general purpose processor, microcode,
PLAs, or ASICs.
[0109] It is also envisioned that embodiments of the invention
could be accomplished as computer signals embodied in a carrier
wave, as well as signals (e.g., electrical and optical) propagated
through a transmission medium. Thus, the various information
discussed above could be formatted in a structure, such as a data
structure, and transmitted as an electrical signal through a
transmission medium or stored on a computer readable medium.
[0110] It is also noted that many of the structures, materials, and
acts recited herein can be recited as means for performing a
function or step for performing a function. Therefore, it should be
understood that such language is entitled to cover all such
structures, materials, or acts disclosed within this specification
and their equivalents, including the matter incorporated by
reference.
[0111] It is thought that the apparatuses and methods of
embodiments of the present invention and its attendant advantages
will be understood from this specification. While the above
description is a complete description of specific embodiments of
the invention, the above description should not be taken as
limiting the scope of the invention as defined by the claims.
* * * * *
References